1. Technical Field
Embodiments of the subject matter disclosed herein generally relate to methods and systems and, more particularly, to mechanisms and techniques for handling heavy components of a device.
2. Discussion of the Background
During the past years, with the increase in price of fossil fuels, the interest in developing new production fields has dramatically increased. However, the availability of land-based production fields is limited. Thus, the industry has now extended drilling to offshore locations, which appear to hold a vast amount of fossil fuel.
The existing technologies for extracting the fossil fuel from offshore fields use a system 10 as shown in FIG. 1. More specifically, the system 10 includes a vessel 12 having a reel 14 that supplies power/communication cords 16 to a controller 18. The controller 18 is disposed undersea, close to or on the seabed 20. In this respect, it is noted that the elements shown in FIG. 1 are not drawn to scale and no dimensions should be inferred from FIG. 1.
FIG. 1 also shows a wellhead 22 of the subsea well and a drill line 24 that enters the subsea well. At the end of the drill line 24 there is a drill (not shown). Various mechanisms, also not shown, are employed to rotate the drill line 24, and implicitly the drill, to extend the subsea well.
However, during normal drilling operation, unexpected events may occur that could damage the well and/or the equipment used for drilling. One such event is the uncontrolled flow of gas, oil or other well fluids from an underground formation into the well. Such event is sometimes referred to as a “kick” or a “blowout” and may occur when formation pressure inside the well exceeds the pressure applied to it by the column of drilling fluid. This event is unforeseeable and if no measures are taken to prevent it, the well and/or the associated equipment may be damaged. Although the above discussion was directed to subsea oil exploration, the same is true for ground oil exploration.
Thus, a blowout preventer (BOP) might be installed on top of the well to seal the well in case that one of the above events is threatening the integrity of the well. The BOP is conventionally implemented as a valve to prevent the release of pressure either in the annular space between the casing and the drill pipe or in the open hole (i.e., hole with no drill pipe) during drilling or completion operations. Recently, a plurality of BOPs may be installed on top of the well for various reasons. FIG. 1 shows two BOPs 26 or 28 that are controlled by the controller 18.
Such plural BOPs assembled together form a BOP stack. A traditional BOP stack may be tens of meters high and weighs tens of thousands of kilograms. Various components of the BOP stack need to be replaced from time to time. An example of the BOP 26 is shown in FIG. 2. The BOP 26 shown in FIG. 2 has, among other things, two ram blocks 30 that are supported by respective piston rods 32. The two ram blocks 30 are configured to move along a direction parallel to a longitudinal axis of the piston rods 32. The ram blocks 30 may severe the drill line 24 or other tools that cross a vertical wellbore 34 of the BOP 26. However, after cutting the drill line 24 for a number of times, the ram blocks 30 and/or their respective cutting edges need to be verified and sometimes reworked. For this reason, the BOP 26 of FIG. 2 is provided with a bonnet 36, for each ram block 30, that can be opened for providing access to the ram blocks. FIG. 2 shows the bonnet 36 having a hinge 38 that rotatably opens the bonnet 36.
FIG. 3 shows the BOP 26 having the bonnet 36 opened so as to expose the ram block 30. As the weight of the ram block may be in excess of 100 kg, sometimes around 400 kg, it would be difficult for one or more persons to remove the ram block 30 from the BOP 26 for maintenance. Thus, a crane may be used to lift and store the ram block 30 in a desired position while undergoing maintenance.
However, the usage of the crane becomes impractical when plural BOPs are assembled to form the BOP stack. The BOP stack has a frame of its own that contains the multiple BOPs. However, the frame of the BOP stack also limits the accessibility of a crane to the BOPs. Further, as the BOPs are disposed on top of each other and one BOP may be as high as a few meters from the floor, it is impractical for maintenance personnel to directly access the BOP components (they are too high to be reachable) even when the BOP stack is in a maintenance facility. In addition, if the ram block has to be replaced while the BOP stack is in the field (e.g., deep under sea or when the BOP stack is brought on the maintenance vessel), it is difficult to use a crane attached to a solid base to remove various components of the BOPs with that crane in order to reach the ram blocks.
Accordingly, it would be desirable to provide systems and methods that avoid the afore-described problems and drawbacks.